Semiconductor lasers based on polycrystalline thin films of ZnO and techniques for pumping them optically are known. The article of H. Cao et al. entitled “Ultraviolet lasing in resonators formed by scattering in semiconductor polycrystalline film” and published in “Applied Physics Letters”, Vol. 73, No. 25, 21, Dec. 1998, pp. 3656-3658, describes such a laser in which resonant cavities are self-formed because of high optical diffusion in the active material. This medium is obtained by growing a polycrystalline thin film of Zinc Oxide on amorphous melted silicon. The active material is optically pumped with a laser beam of 355 nm obtained by using a frequency tripling a locked mode YAG-Nd laser. The laser emission is ultraviolet, at about 380 nm.
The article by Z. K. Tang et al. entitled “Room-temperature ultraviolet laser emission from self-assembled ZnO microcrystalline thin film” and published in the journal “Applied Physics Letters”, Vol. 72, No. 25, 22, Jun. 1998, pp. 3270-3272 describes a laser comprised of hexagonal ZnO microcrystallites obtained by MBE (“Molecular Beam Epitaxy”). These microcrystallites are auto-assembled in the form of a matrix on a sapphire substrate. In this case, also, pumping is performed optically using a frequency tripled YAG-Nd laser.
The optical pumping of these structures is complex and makes them difficult to use. It would, therefore, be advantageous to provide a simpler structure that is easier to use.